Added lookup_struct_test.cu which tested various ways for doing faster neighbor lookups. The best tested method is simpley the N2 check every particle against every other method.
Added lookup_struct_test.cu which tested various ways for doing faster neighbor lookups. The best tested method is simpley the N2 check every particle against every other method.

cschenck/SmoothParticleNets,cschenck/SmoothParticleNets,cschenck/SmoothParticleNets